E. THE SMALL INTESTINE, BY E. VERSON. 561 



cordance with the direction of the fibres composing each, into 

 an external longitudinal, and an internal circular. The former 

 pursues the same direction as the intestine itself, the latter runs 

 more or less at right angles to it, and embraces it with circular 

 or spiral coils. A few fibres deviate from these two main 

 directions, coursing round the muscular tube in a radial or 

 oblique direction. Such fibres are occasionally found united 

 into thick fasciculi in the upper portion of the duodenum, 

 close to the pylorus, and they may be followed from thence, 

 forming compressed spirals, into the longitudinal layer of the 

 duodenum. 



The muscular tube of the small intestine progressively 

 diminishes in thickness towards the iliocaecal valve, the atte- 

 nuation being particularly observable in the longitudinal layer, 

 which in some of the lowermost parts may even be altogether 

 deficient. The circular is generally thicker than the longitudi- 

 nal layer, amounting in the adult to about 0'2 to 0*3 of a milli- 

 meter, whilst the longitudinal layer scarcely exceeds O'l of a 

 millimeter in thickness. This proportion may, however, be 

 reversed, strata of the longitudinal fibres being here and there 

 found with corresponding diminution of the circular fibres. 



The anterior surface of the duodenum is covered, as is well 

 known, by a single layer of peritoneum, whilst the posterior 

 surface is uncovered. At the lower curvature it is attached to 

 the abdominal wall by an organic muscle, to which Treitz * has 

 applied the name of Suspensorius duodeni. This consists of 

 a few fasciculi of the longitudinal layer, terminating in 

 tendinous fibres, that accompany the dense connective tissue 

 surrounding the caeliac and mesenteric arteries, and are then 

 lost. The fasciculi increase remarkably in breadth, and whilst 

 they do not exceed two to three millimeters in thickness, are 

 almost ten times that breadth. Additional fasciculi not unfre- 

 quently join them, derived from the diaphragm (right border of 

 the foramen cesophageum and internal crua). 



The duodenum has yet another muscular attachment at the 

 head of the pancreas. In the duodenum of the child I find 



* Ueber Einen neuen Muskel am Duodenum des Menschen, " On a New 

 Muscle of the Duodenum in Man." Prager Vierteljahresschrift, Band i. 



